class_docstr: Mixin that aggregate states of children.
  
  This mixin can only applied to chainer.Chain or chainer.ChainLink. The
  resulting class will implement Recurrent by searching recurrent models
  recursively from its children.
code: def get_state(self):
      return get_state(self)
  
imports: from abc import ABCMeta
  from abc import abstractmethod
  import collections
  import contextlib
  import chainer
label_desc: Use image node_id 1 for calling the RecurrentChainMixin obj's underlying member method code with example usage: obj.get_state() and returns: get_state